Since an optical communication system using an optical fiber serving as one of optical waveguides, wavelength dispersion of the optical fiber considerably affects the characteristics of the optical communication system to distort a signal waveform in propagation of an optical signal, it is indispensable in design of the communication system that wavelength dispersion of the optical fiber or the like is known by measurement. In particular, in an actual operation or a test of a system, when an optical cable is installed, distribution of optical fibers in a direction of length of wavelength dispersion must be often measured. In this manner, as a method of non-destructively measuring a distribution of optical fibers in the direction of length of wavelength dispersion, a conventional method of using optical four-wave mixing in optical fibers is given (for example, see Non-patent Document 1).
Non-patent Document 1: L. F. Mollenauer et al. “Method for facile and accurate measurement of optical fiber dispersion maps, “OPTICS LETTERS, VOL. 21, NO. 21, Nov. 1, 1996, pp. 1724-1726
Non-patent Document 2: E. Brinkmeyer and R. Ulrich, “High-resolution OCDR in dispersive waveguides, “Electronics Letters, vol. 26, No. 6, pp. 413-414 (15 Mar. 1990)